The present invention relates generally to computed tomography imaging and, more particularly, to an apparatus and method of converting x-rays to light energy for use with computed tomography systems.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward an object, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the object. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing unit for analysis which ultimately results in the formation of an image.
Generally, the x-ray source and the detector array are rotated with a gantry within an imaging plane and around the object. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator.
In one known CT imaging system, each scintillator of a detector array comprises thallium-based cesium iodide (CsI:TI). Thallium-based cesium iodide and other scintillator compositions such as gadolinium sulfate (Gd(SO3)) have significant light output. However, thallium-doped cesium iodide, gadolinium sulfate, and other known scintillator compositions achieve approximately 90% decay in approximately 3-1000 microseconds. This delay in decay results in residual effects that oftentimes cause inefficient light emission and detection, and overall poor performance of the CT system.
It would therefore be desirable to have a scintillator with sufficient light output, but reduced decay time.
The present invention provides a detector for a CT imaging system and method of use that solves the aforementioned drawbacks. The detector includes a focused scintillator for receiving and converting high frequency electromagnetic energy to light energy. The detector further includes a photodiode positioned adjacent to the scintillator and is configured to receive light energy discharged through a light exiting surface of the scintillator. The detector also includes electrical leads connected from the photodiode to a data processing unit. Signal outputs of the photodiodes are transmitted to the data processing unit to facilitate image reconstruction. The CT system provides for a gantry having an output for projecting high frequency electromagnetic energy toward the tapered scintillator.
In accordance with one aspect of the invention, a detector including a scintillator array is provided. The scintillator array includes at least one scintillator comprising lutetium orthosilicate. The scintillator receives high frequency electromagnetic energy and converts that energy to light energy. A photodiode array comprising at least one photodiode is optically coupled to the scintillator array and is configured to detect light output of the scintillator. Each photodiode of the photodiode array produce outputs that are transmitted by a plurality of electrical interconnects to a data acquisition system.
In accordance with another aspect of the invention, a computed tomography system is provided. The system includes a rotatable gantry having an opening and a high frequency electromagnetic energy projections source capable of projecting high frequency energy toward an object. A scintillator array includes a plurality of scintillators each comprising lutetium orthosilicate and receives the high frequency electromagnetic energy attenuated by the object. A photodiode array is optically coupled to the scintillator array and is configured to detect light energy emitted therefrom. The photodiode array produces outputs that are transmitted to a data processing system by a plurality of electrical interconnects. The system further includes a computer capable of producing a visual display based upon the photodiode outputs transmitted to the data processing system.
In accordance with yet another aspect of the invention, a method of computed tomography imaging is provided. The method includes the steps of providing a scintillator array having a plurality of scintillators wherein each scintillator comprises lutetium orthosilicate. The method further includes directing high frequency electromagnetic energy to the scintillator array and coupling a photodiode array having a plurality of photodiodes to the scintillator array. The method also includes the step of discharging light energy from the scintillator array to the photodiode array and transmitting photodiode output to a data processing system for image construction. The method further includes displaying a constructed image based on the photodiode output transmitted to the data processing system for image construction.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.